Tokkai Hei 09-105458 published by the Japan Patent Office in 1997 discloses increasing an engine output torque to decrease a speed change shock during downshift of a stepwise automatic transmission of a vehicle.
In this prior art technique, a speed change shock is prevented by making the engine output torque increase from when one clutch starts to disengage one gear until another clutch starts to engage another gear. Specifically, in the prior art, the engine output torque for attaining the engine rotation speed after the downshift is calculated, and engine control is performed so that the calculated output torque is obtained. In the following description, this output torque will be referred to as a rotation synchronous torque.